Process for desulfurization of aromatics

ABSTRACT

THE SULFUR-PARTICULARLY THAT PRESENT AS THIOPHENESCONTAINED IN AROMATIC HYDROCARBONS IS SUBSTANTIALLY REMOVED BY TREATING THE HYDROCARBONS WITH METALS, AND OXIDES THEREOF HAVING HYDROGENATING ACTIVITY. IN ONE EMBODEMENT, THE AROMATIC HYDROCARBON IS CONTACTED WITH NICKEL, COBALT, NICKEL AND TUNGSTEN, COBALT AND TUNGSTEN, OR THEIR OXIDES AT A TEMPERATURE OF ABOUT 200 TO 600*F. AND A PRESSURE OF ABOUT 50-500 P.S.I.G. IN ANOTHER EMBODIMENT, THE AROMATIC HYDROCARBON IS CONTACTED WITH NICKEL, COBALT, NICKEL AND MOLYBDENUM, COBALT AND MOLYBDENUM, NICKEL AND TUNGSTEN, COBALT AND TUNGSTEN, OR THEIR OXIDES AT A TEMPERATURE OF ABOUT 600-900*F. AND A PRESSURE OF ABOUT 0-50 P.S.I.G.

United States Patent 3,642,927 PROCESS FOR DESULFURIZATION F AROMATICSStephen M. Kovach, Ashland, and Ralph E. Patrick,

Flatwoods, Ky., assignors to Ashland Oil & Refining Company, Houston,Tex.

Filed Feb. 7, 1968, Ser. No. 703,585 Int. Cl. C07c 7/00 US. Cl. 260-67418 Claims ABSTRACT OF THE DISCLOSURE The sulfur-particularly thatpresent as thiophenescontained in aromatic hydrocarbons is substantiallyremoved by treating the hydrocarbons with metals, and oxides thereofhaving hydrogenating activity. In one embodiment, the aromatichydrocarbon is contacted with nickel, cobalt, nickel and tungsten,cobalt and tungsten, or their oxides at a temperature of about 200 to600 and a pressure of about 50-500 p.s.i.g. In another embodiment, thearomatic hydrocarbon is contacted with nickel, cobalt, nickel andmolybdenum, cobalt and molybdenum, nickel and tungsten, cobalt andtungsten, or their oxides at a temperature of about 600-900 F. and apressure of about 0-50 p.s.i.g.

FIELD OF THE INVENTION The present invention relates to the purificationof aromatic hydrocarbons. In a more specific aspect, the presentinvention relates to the removal of sulfur compounds from aromatichydrocarbons. In a still more specific aspect, the present inventionrelates to the removal of thiophene and alkylated thiophenes fromaromatic hydrocarbons.

SUMMARY OF THE PRIOR ART The commercial demand for monoand polycyclicaromatics, such as benzene and naphthalene, is wellknown to thoseskilled in the art. It is equally well-known that the commercial valueof such monoand polycyclic hydrocarbons resides to a large extent in thepurity of the material. For example, high purity naphthalene is used asan intermediate in the production of phthalic anhydride, which requireshigh purity naphthalene. Similarly, the chemical industry requires highgrade benzene for nitration and like treatments.

At the present time, the vast majority of naphthalene and a considerableportion of the benzene produced in the United States is obtained by thedistillation of coal tar products. The coal tar products are generallyproduced as a by-product of the high temperature carbonization of coalto yield coke. Another source of such coal products is the solventextraction of coal to yield hydrocarbon liquids and combinations ofsolvent extraction and carbonization. Monoand polycyclic hydrocarbonsare also present in crude petroleum. While the amounts present in crudepetroleum vary with the source, the total amount of all aromatichydrocarbons in crude petroleum is only about Separation byfractionation of the desired aromatics from crude petroleum has notproven feasible because of the large volumes of other hydrocarbons,boiling in substantially the same range, which are present in the crude.However, certain fractions of petroleum products, from processes such ascatalytic reforming, catalytic cracking, and thermal cracking, docontain significant amounts of monoand polycyclic aromatics which can beeconomically recovered.

Hydrocarbon fractions rich in monocyclic and polycyclic aromatics,particularly those derived from coal, contain rather substantial volumesof impurities, particularly sulfur compounds, such as thiophenes, alkylthiophenes,

3,642,027 Patented Feb. 15, 1972 thionaphthenes, etc. These compoundscomplicate the recovery and purification of monoand polycyclicaromatics, since they display boiling points close to the desiredhydrocarbons. In order to produce chemical grade monocyclic andpolycyclic aromatics, such as benzene and naphthalene, these sulfurcompounds, as well as nitrogen compounds and small amounts ofnon-aromatic hydrocarbons, must be removed from the product or theircontents be substantially reduced. For example, chemical grade benzenespecifications require 0.5 ppm. thiophene or less. Similarspecifications apply to chemical grade naphthalene.

Benzene in coal liquids is concentrated in what is usually referred toas a light oil fraction. This light oil is high in benzene, toluene, andxylene, but contains high concentrations of sulfur and nitrogencompounds and small amounts of non-aromatics. The coal tar light oilsare generally considered to be coal liquids boiling up to about 400 F.,but more generally such liquids boiling up to about 340 F. to 360 F.Commercially, these light oils have been processed to recover benzene,toluene and xylene by hydrotreating, followed by solvent extraction,such as extraction with a triethylene glycol-water system or byhydrotreating followed by hydrodealkylation. The hydrodealkylation, inaddition to removing alkyl groupsfrom the toluene and xylene, and thusincreasing benzene production, also serves to remove a portion of thesulfur impurities when certain types of catalytic hydrodealkylationschemes are utilized. However, the product of such adealkylation-desulfurization unit still contains from 1 to 50 andgenerally 1 to 2 ppm. of thiophene, all of which are over thespecification for commercial grade benzene. Similar low-boiling refinerystreams are also treated by similar tion of coal liquids boiling abovethe previously mentioned light oil and below the pitch or tar fractions.This broad boiling range can be from about 340 to about 680 F. However,as a practical matter, it is highly desirable that a heart-cut of thisso-called middle oil, boiling between about 400 and 600 F., be utilizedas a source of naphthalene. This out also contains the usual sulfur andnitrogen contaminants as well as alkyl naphthalenes. Consequently, thefraction is generally treated in essentially the same way as the lightoil fraction in order to pro duce substantial quantities of high puritynaphthalene. In other words, the ideal treatment is the previouslymentioned deal'kylation-desulfurization treatment. However, as is thecase with the benzene product of the dealkylation-desulfurizationtreatment, the naphthalene product also contains undesirable quantitiesof thiophenes and alkyl thiophenes which must be removed orsubstantially reduced in amount. These products, however, also containtrace quantities of indene or indan compounds which cause discolorationof the product and make it undesirable as a commercial gradenaphthalene. In accordance with conventional practice, thisdiscoloration may be remedied by subjecting the product to treatmentwith hot clay at temperatures between about 450 to 500 F. While this hotclay treatment has been found effective in removing non-sulfurcontaminants, it has been found ineffective in the removal of the sulfurcompounds previously mentioned.

-In addition to the hot clay treatment previously mentioned, severalother schemes have been investigated for the removal of thiophene andalkyl thiophenes from monocyclic and polycyclic aromatics. One of theseinvolves a sodium treatment with a sodium dispersion or a sodiumimpregnated clay. This technique has numerous drawbacks, the principalof which is the presence of water and olefins which lead to high sodiumconsumption. The aromatic products can also be treated with acid, suchas sulfuric acid, and the sulfur compounds effectively removed in thismanner. However, the recovery of aromatics is quite low since it iswell-known that the sulfuric acid treatment of aromatics is effective inthe production of aromatic sulfonates. Desulfurization has also beenpracticed under conventional desulfurization conditions, i.e., atrelatively high temperatures and pressures and at low space velocities,as by the commonly hydrotreating process. While such treatments arehighly successful for the removal of thiophene and thiophene compounds,this process, as commercially practiced, is uneconomical. If aplatinum-containing catalyst is utilized, complete desulfurization canbe obtained, but the aromatic products are also hydrogenated, therebyproducing contaminating amounts of cyclohexenes, methylcyclopentanes,etc. It would, of course, also be effective to re-process the materialproduced in the previously-mentioned dealkylationdesulfurizationoperation in a similar unit, or to treat relatively pure benzene andnaphthalene produced by the other techniques in adealkylation-desuliurization unit. However, by the time products of thepurity referred to herein have been produced by any of the previouslyoutlined methods, it is wholly uneconomical to process these productsthrough a hydrodealkylation unit.

SUMMARY OF THE INVENTION In view of the above, it is an object of thepresent invention to provide an improved process for the production ofpurified aromatic hydrocarbons. Another and further object of thepresent invention is to provide an improved process for the productionof aromatic hydrocarbons by the removal of sulfur compounds therefrom.Yet another object of the present invention is to provide an improvedprocess for the removal of sulfur compounds from monocyclic andpolycyclic aromatic hydrocarbons. Another and further object of thepresent invention is to provide an improved process for the removal ofthiophenes and alkyl thiophenes from aromatic hydrocarbons. Stillanother object of the present invention is to provide an improvedprocess for the purification of benzene, naphthalene, and like monoandpolycyclic aromatic hydrocarbons. A still further object of the presentinvention is to provide an improved process for the removal ofthiophenes and alkyl thiophenes from high purity benzene, naphthaleneand like monocyclic and polycyclic aromatic hydrocarbons. Yet anotherobject of the present invention is to provide an improved process forpurification of monocyclic and polycyclic aromatic hydrocarbons withoutdestruction of the aromatic compounds themselves. A further object ofthe present invention is to provide an improved process for the removalof small amounts of thiophenes and alkyl thiophenes from monocyclic andpolycyclic aromatic hydrocarbons, such as benzene and naphthalene,without the consequent loss of a portion of the aromatics. Another andfurther object of the present invention is to provide an improvedprocess for the removal of thiophene and alkyl thiophenes frommonocyclic and polycyclic hydrocarbon streams, such as benzene andnaphthalene streams containing less than 100 ppm. of such thiophenes,wherein the hydrocarbon stream is catalytically treated under conditionsfor the removal of the thiophenes without the consequent hydrogenationof the aromatic materials. A yet further object of the present inventionis to provide an improved process for the purification of aromatichydrocarbons comprising subjecting the hydrocarbon to adealkylationdesulfurization reaction and thereafter removingsubstantially all of the sulfur contaminants remaining withouthydrogenation of the aromatics. These and other objects and advantagesof the present invention will be apparent from the followingdescription.

Briefly, in accordance with the present invention, aromatic hydrocarbonscontaining small amounts of sulfur compounds are subjected to treatmentwith a hydrogeneation-dehydrogenation metal catalyst, particularly ametal selected from the group consisting of nickel, cobalt, or mixturesof these metals with molybdenum or tungsten,

under conditions such that the sulfur compounds are removed withouthydrogenation of the benzene nucleus of the aromatic hydrocarbons. Wherethe feed material is treated at a high temperature, in the presence ofthe specified catalysts, essentially atmospheric pressure is maintainedand small amounts of hydrogen are added from an external source and highvelocities are employed; whereas, treatment at lower temperaturesrequired high pressurees and no external hydrogen introduction. In thepreferred operation, the aromatic hydrocarbons contain alkyl aromatichydrocarbons and the aromatic hydrocarbons are first subjected to adealkylation treatment to produce a material concentrated in aromatics,with substantially no non-aromatics, and relatively small amounts ofsulfur compounds. Therefter, the dealkylation product is subjected tothe previously-mentiened treatment with a hydrogenation-dehydrogenationcatalyst under select conditions for the removal of the remaining sulfurcompounds without hydrogenation ef the aromatic compounds.

The details of the present invention will be set forth with specificreference to the single sheet of drawings, which represents a typicalflow diagram for carrying out the preferred process of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the drawing, afeed material is introduced through line 10 to hydrodealkylation reactor12. The total product of hydrodealkylation reactor 12 is dischargedthrough line 14 to condenser 16. The effiuent of condenser 16 passesthrough line 18 to fractionator 20. In fractionator 20, thehydrodealkylation product is separated into a gas, which is dischargedthrough line 22, a bottoms product or heavy oil, suitable for use as afuel or for a variety of other purposes, and a concentrated aromaticproduct. The bottoms product is discharged through line 24 while theconcentrated aromatic is discharged through line 26. Whether theconcentrated aromatic product be benzene or naphthalene or some otheraromatic product, it still contains undesirable quantities of impuritieswhich must be removed to produce chemical grade aromatics. In order toremove certain of these impurities, the product is subjected to a hotclay treatment in hot clay treater 28. In the hot clay treater 28, thearomatic product is treated at a temperature of about 450 to 500 F. toremove indenes, indan and like contaminants. Partially purified aromaticproduct, which yet contains thiophenes and alkyl thiophenes in amountsof 1 to 50 parts per million or even higher, is discharged through line30. The partially purified aromatic then passes to desulfurization unit32, where it is treated with a hydrogenation-dehydrogenation catalyst,under select conditions as set forth herein, to remove substantially allof the remaining sulfur compounds. The purified aromatic is thendischarged through line 34 to storage or other receptacle for use orsale. In those instances where hydrogen is added to the desulfurizationreactor, such addition is through line 36. This hydrogen may be derivedfrom a wide variety of refinery gases, including the off gas ofhydrodealkylation unit 12.

The feed material to hydrodealkylation unit 12 may be derived from anysource of hydrocarbonaceous material, including coal, petroleum, etc.For example, coke oven or coal tar oils and pitches derived from thecarbonization of coal, liquids extracted from coal by solvent extractionwith Tetralin, Decalin, etc., and liquids obtained by combinations ofsolvent extraction and carbonization may be uti lized. As previouslyindicated, these liquids may be further concentrated by fractionation orlike separations to obtain a feed rich in benzene or a feed rich innaphthalene. The feed material to the hydrodealkylation unit 12 may alsobe a process stream from a petroleum or coal refinery, such as catalyticreformate, obtained by contacting petroleum or coal liquids with aprecious metal catalyst, such as platinum, at a temperature of about 900to 950 F., a pressure of about 200 to 600 p.s.i.g., at a weight hourlyspace velocity between about 1.5 and 5, and using ahydrogen-to-hydrocarbon ratio between about 3 to 1 and to 1. Thelower-boiling fraction of reformate boiling below about 400 F. is thepreferred feed when benzene is to be the end product; whereas, areformate fraction boiling between about 400 and 600 F. is the preferredfeed when naphthalene is the preferred product. The reformer product maybe further treated prior to introduction to the hydrodealkylationreactor, as by solvent extraction, such as with a triethyleneglycol-water solvent system, or by other known means of concentration.Other petroleum fractions which may be used as a feed for thehydrodealkylation unit may include kerosene which has been extractedwith an aromatic selective solvent, such as sulfur dioxide, a catalyticcracking light cycle oil, such light cycle oils which have beensubjected to solvent extraction, as with sulfur dioxide, orhydrocracking or a similar light cycle oil from a thermal crackingoperation.

Hydrodealkylation unit 12 is preferably a catalytic hydrodealkylationunit utilizing a catalyst and operating under conditions such that itnot only concentrates the desired aromatic and produces additionalamounts thereof, but also clarifies and desulfurizes the product. Apreferred catalyst operation of this type is one carried out in thepresence of a catalyst containing from 10 to about of chromia on a gammaalumina carrier. A highly effective catalyst of this character isdesignated G-41 by its manufacturer, the Girdler Corporation ofLouisville, Ky. When utilizing such a catalyst, the hydrodealkylationmay be carried out at temperatures between about 1000 and 1400 F.,preferably between about 1250 and 1300 F.; at a pressure of about 100 to1000 p.s.i.g., and preferably between 400 and 1000 p.s.i.g.; at a weighthourly space velocity between about 0.5 and 5, and preferably betweenabout 0.5 and 3; and at a hydrogen-to-hydrocarbon ratio between about 3and 10' moles of hydrogen per mole of hydrocarbon, and preferablybetween about 6 and 7 to 1. It is possible to carry out thehydrodealkylation without a catalyst, in which case the temperature isabove about 1200 F., the pressure above about 500 p.s.i.g., and thehydrogen-to-hydrocarbon ratio is about 1400 to 1900 cubic feet ofhydrogen per barrel of feed. However, the catalytic operation has beenfound to be substantially more effective.

The product of the hydrodealkylation unit includes a normally gaseousmaterial and a normally liquid material. The residual light gases aredrawn OE and used as a plant fuel or in variety of other manners. Thehighest boiling or bottoms product, boiling above the boiling point ofthe desired concentrated aromatic, is normally drawn off and utilized asa fuel oil stock. The cut point between the concentrated aromatic andthe bottoms fraction depends primarily on the type of feed andconsequently upon the concentrated aromatic to be recovered. Whenbenzene is the desired concentrated aromatic, the cut point would beabout 300 to 350 F. Where naphthalene is the primary end product, thecut point should be about 400 to 600 F., and ideally 440 to 525 F.

As previously pointed out, the concentrated aromatic product isessentially free of non-aromatic materials but contains minor amounts ofcontaminants, despite the highly eifective nature of thehydrodealkylation reaction. Therefore, in order to remove certain ofthese contaminants, it is desirable to subject the concentrated aromaticto a hot clay treatment. In this hot clay treatment, the maerial issubjected to temperaures of about 450 to 550 F., and certain of thecontaminants are adsorbed on the clay. This is a known process andtherefore will not be discussed in any great detail. The hot claytreatment removes substantially all of the non-sulfur containing,contaminating materials from the partially purified aromatic but failsto remove the small amounts of thiophene and alkylated thiophenes whichare still present in the aromatic and render it unfit as a chemicalgrade product. Consequently, the partially purified aromatic issubjected to the selective desulfurization reaction which forms asignificant step in the present process.

In the desulfurization reactor 32, the partially purified aromatic iscontacted with a hydrogenation-dehydrogenation metal catalyst underconditions selective to the removal of the sulfur compounds butineffective to hydrogenate any of the aromatic present.

One of the primary factors in the novel process of the present inventionis the utilization of a specific group of hydrogenation-dehydrogenationcatalysts in desulfurization reactor 32. Any activehydrogenation-dehydrogenation catalyst, such as, platinum, rhodium,palladium, nickel, cobalt, etc., may be used. While the precious metalsof this group are adequate, the amounts necessary for long on-streamperiods limit their use from an eco nomic standpoint. However, it hasbeen found that excellent results in the removal of thiophene fromaromatics can be obtained by utilizing a catalyst selected from thegroup consisting of nickel, cobalt, and mixtures of these metals withmolybdenum and tungsten. Preferably the metal is deposited on an inertcarrier material, such as kieselguhr, alumina, silica-alumina, etc. Suchcatalysts are relatively inexpensive, can be pro-reduced or in theiroxide state and, therefore, reduced during the operation to the extentthat hydrogen is present to effect such reduction. The metal should bepresent on the carrier in amounts ranging from about 1 to 60% by weight.However, in order to guarantee long cycle time, it is necessary to havefrom 10 to 60% and preferably between about 10 and 55% by weight. Whileit is not desired to be limited to any particular theory of operation,it is believed that the metal, in its free metal state, combines withthe sulfur compounds to eventually form metal sulfides and olefins. 'Ifa low concentration of hydrogen is also present during the reaction, theolefins will be converted to saturates which can be more readilyremoved. The spent metal sulfide may be effectively restored to itsoriginal activity by air regeneration and reduction of the metal oxidewith hydrogen to the free metal state. To confirm this theory ofoperation, a nickel catalyst was converted to nickel sulfide bytreatment with hydrogen sulfide and the sulfided catalyst was testedunder the process conditions of this invention for the removal ofthiophene. The thiophene content of the product remained unchanged andat times was greater than that in the feed. Consequently, it appearsthat the postulated conversion of the metal to metal sulfide is theprimary mechanism by which the sulfur is removed from the aromaticproduct. By the same token, however, under the conditions practicedherein, no hydrogenation of the aromatic product occurs.

While the conditions of operation of the desulfurization reactor mayvary over rather wide ranges, these conditions are critical to theoperation and certain of the conditions are critically interdependentupon one another. More specifically, the temperature of the operationmay vary from about 200 to 900 F.; the pressure may vary from 0 to 500p.s.i.g.; the liquid hourly space velocity may be between about 0.1 and10; and the hydrogen-tohydrocarbon ratio may vary from 0 to 1. Since theprimary purpose of the treatment is to convert the metallichydrogenation-dehydrogenation catalyst to a metal sulfide and to avoidany appreciable hydrogenation of the aromatic being treated, thetemperature of operation has been found to be a critical factor. If thetemperature is maintained between about 200 and 600 F., or a matter ofconvenience, between about 450 and 500 F., (the usual temperature of theproduct passing from the hot clay treating operation), the pressure ofthe operation should be at the higher limits, usually between about 50to 500 p.s.i.g., and no hydrogen should be added from an externalsource. The following example will illustrate an operation of thischaracter.

A hydrodealkylation benzene product containing about 5 ppm. of thiophenewas treated with a catalyst comprising 55% nickel oxide deposited on akieselghur carrier. The catalyst was first reduced with hydrogen at atemperature of about 450 F. and under presusre. The benzene product wasthen processed over the catalyst at a temperature of about 450 F., at apressure of about 400 p.s.i.g., while maintaining a liquid hourly spacevelocity of about 4, and without the addition of hydrogen from anexternal source. The product of this treatment was analyzed and found tocontain 0.7 p.p.m. of thiophene. This, of course, represents the removalof about 86% of the original thiophene, and, based on the data set outin the other examples given herein as well as related work, a benzeneproduct containing from 1.5 to 2% thiophene would be reduced to aproduct containing about 0.2 p.p.m. of thiophene.

Where the monocyclic or polycyclic aromatic to be desulfurized can beconveniently heated to a higher temperature, desulfurization at suchhigher temperature has certain advantages. For example, no aromatichydrogenation will occur at temperatures between about 600 and 900 F.,and preferably between about 650 and 750 F., even in the presence ofsmall amounts of hydrogen from an external source. The hydrogen should,of course, be added in extremely low concentrations sufficient only toconvert olefins produced by the desulfurization to saturates and to theextent that the hydrogenation-dehydrogenation metal is in its oxide formto reduce the oxide to free metal. It has been found that this can beaccomplished in accordance with the present invention by utilizing ahydrogen-to-hydrocarbon mole ratio between about 0.01 to 1 to 1, andpreferably between about 0.1 and 1 to 1. At these high temperatures, theoperation should also be carried at essentially atmospheric pressure,the only pressure, therefore, being that sufficient to introduce theexternal hydrogen. Accordingly, a pressure of about p.s.i.g. would beemployed, but may range up to about 50 p.s.i.g. As previously indicated,the liquid hourly space velocity may vary from 0.1 to 10, and preferablyshould be between about 1 and 5.

The results of three such high temperature treatments are illustrated inthe following Table I. In these three runs, benzene from ahydrodealkylation unit had added thereto varying amount of thiophene, asindicated in the table. The material was then contacted with theindicated catalyst under the conditions set forth in the table.

Conditions:

Tempcrature, F." 700-730 730. 740 Pressure, p.s.l.g 0 0 0 LHSV 1 1H2/HC,molc/mole 1/3 1/3 1/3 Product: Thlophene, 0.09 0.9 1

p.p.m.

The results of Table I above indicate that 99% desulfurization wasobtained irrespective of the amount of thiophene contained in thesample. Consequently, it can readily be observed that in order to obtainan aromatic product containing less than 0.5 p.p.m. of thiophene from acontaminated product, the product may contain up to 50 p.p.m. ofthiophene. Such a product, as previously indicated, will meet chemicalgrade specifications after treatment in accordance with the presentinvention.

Having described the present invention with reference to a specific flowdiagram and specific examples, it is to be understood that these areillustrative only and that the invention is to be limited only inaccordance with the appended claims.

We claim:

1. A method for the purification of aromatic hydrocarbons containingsmall amounts of thiophenes, alkyl thiophenes and thionaphthenes,comprising, contacting said aromatic hydrocarbons with ahydrogenation-dehydrogenation metal catalyst selected from the groupconsisting of oxides and free metals of metals selected from the groupconsisting of nickel, cobalt, mixtures of nickel with tungsten andmixtures of cobalt with tungsten, under conditions sufiicient to convertsaid thiophenes, alkyl thiophenes and thionaphthenes to metal sulfidesand olefins, to dehydrogenate sufficient of said aromatic hydrocarbonsto hydrogenate said olefins, to hydrogenate said olefins and to preventhydrogenation of said aromatic hydrocarbons including, a temperature ofabout 200 to 600 F., a pressure of about 50 to 500 p.s.i.g., a liquidhourly space velocity of about 0.1 to 10 and in the absence of hydrogenfrom an external source.

2. A method in accordance with claim 1 wherein the aromatic hydrocarbonsadditionally contain substantial quantities of alkyl aromatichydrocarbons and said aromatic hydrocarbons are first subjected todealkylation conditions suflicient to convert substantially all of saidalkyl aromatic hydrocarbons to unsubstituted aromatic hydrocarbons.

3. A method in accordance with claim 2 wherein the dealkylationconditions are selected to remove a part of the thiophenes, alkylthiophenes and thionaphthenes from the aromatic hydrocarbons.

4. A method in accordance with claim 2 wherein the dealkylation iscarried out in the presence of a dealkylation catalyst.

5. A method in accordance with claim 4 wherein the dealkylation catalystcomprises 10 to 15% chromia deposited on a gamma alumina carrier.

6. A method in accordance with claim 1 wherein the sulfur compounds arethiophenes in amounts less than about p.p.m.

7. A method in accordance with claim 1 wherein the aromatic hydrocarbonsare derived from a solid carbonaceous material.

8. A method in accordance with claim 7 wherein the solid carbonaceousmaterial is coal.

9. A method in accordance with claim 1 wherein the aromatic hydrocarbonsare derived from crude petroleum.

10. A method for the purification of aromatic hydrocarbons containingsmall amounts of thiophenes, alkyl thiophenes and thionaphthenes,comprising, contacting said aromatic hydrocarbons with ahydrogenation-dehydrogenation metal catalyst, selected from the groupconsisting of oxides and free metals of metals selected from the groupconsisting of nickel, cobalt, mixtures of nickel with molybdenum,mixtures of cobalt with molybdenum, mixtures of nickel with tungsten,and mixtures of cobalt with tungsten, under conditions sufficient toconvert said thiophenes, alkyl thiophenes and thionaphthenes to metallicsulfides and olefins, to saturate said olefins and to preventhydrogenation and dehydrogenation of said aromatic hydrocarbons,including, a temperature of about 600 to 900 F., a pressure of about 0to 50 p.s.i.g., a liquid hour- 1y space velocity of about 0.1 to 10, andin the presence of hydrogen, from an external source, in amounts ofabout 0.01 to 1 mol hydrogen per rnol of aromatic hydrocarbons.

11. A method in accordance with claim 10 wherein the aromatichydrocarbons additionally contain substantial quantities of alkylaromatic hydrocarbons and said aromatic hydrocarbons are first subjectedto dealkylation conditions sufficient to convert substantially all ofsaid alkyl aromatic hydrocarbons to unsubstituted aromatic hydrocarbons.

12. A method in accordance with claim 11, wherein the dealkylationconditions are selected to remove a part of the thiophenes, alkylthiophenes and thionaphthenes from the aromatic hydrocarbons.

13. A method in accordance with claim 11 wherein the dealkylatiori iscarried out in the presence of a dealkylation catalyst.

14. A method in accordance with claim 13 wherein the dealkylationcatalyst comprises 10 to 15% chromia deposited on a gamma aluminacarrier.

15. A method in accordance with claim 10 wherein the sulfur compoundsare thiophenes in amounts less than about 100 p.p.m.

16. A method in accordance with claim 10 wherein the aromatichydrocarbons are derived from a solid carbonaceous material.

17. A method in accordance with claim 16 wherein the solid carbonaceousmaterial is coal.

18. A method in accordance with claim 10 wherein the aromatichydrocarbons are derived from petroleum.

References Cited UNITED STATES PATENTS 2,951,034 8/ 1960 Stuart 208-2442,951,886 9/1960 Paulsen 260-674 3,198,846 8/1065 Kelso 260-6723,222,410 12/1965 Swanson 260-672 3,310,592 3/1967 Fukuda et a1 260-6723,116,234 12/ 1963 Douwes ct a1. 260-674 3,484,367 12/1969 Winsor260-674 10 OTHER REFERENCES Emmett, Catalysis, vol. V, Reinhold Pub.Corp., New York, 1958, pp. 444 and 445.

Horne et al., Advances in Petroleum Chemistry and Refining, vol. 3,Interscience Publishers, Inc., New York, 1960, pp. 215-217, 225-227.

Gully et al., Advances in Petroleum Chemistry and Refining, vol. 7,Interscience Publishers, Inc., New York, 1963, pp. 248-249, 260-269.

Elgin et al., Industrial and Engineering Chemistry, vol. 22, No. 12, pp.1284-1290.

Elgin, Industrial and Engineering Chemistry, vol. 22, No. 12, pp.1290-1293.

Ellis, The Chemistry of Petroleum Derivatives (1934), TP690E5, pp.461-463.

CURTIS R. DAVIS, Primary Examiner US. Cl. X.R.

